<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="content-type" content="text/html;charset=UTF-8">
    <title>css1</title>
    <style type="text/css">
        body {
            background-color:yellow
                }
        h1{
            background-color:#00ff00
        }
        h2{
            background-color: transparent
        }
        p{
            background-color:rgb(250,0,255)
        }
        .no2{
            background-color:gray;padding:20px;
        }
    </style>

</head>
<body>
<h1>这是标题1</h1>
<h2>这是标题2</h2>
    <p>这是段落</p>
    <p class="no2">这个段落设置了内边距</p>

</body>
</html>